Devices suitable for use in removing modular electronic components from a substrate such as a printed circuit board include those which supply heat to solder which is to be melted, and then remove the molten solder by application of vacuum. The speed with which the solder removal takes place is important in successful removal of, for example, electronic components from printed circuit boards because quick removal of the solder promotes removal of as much of the solder that can be removed. With slow removal, it is more difficult to remove the solder. Moreover, slow removal tends to result in clogging of the molten solder removal path.
An example of a desoldering tool known in the prior art is that in U.S. Pat. No. 3,392,897, which is illustrated in prior art FIG. 1. The present invention is usable with such a desoldering tool such as that shown in prior art FIG. 1, which is briefly described as follows. The desoldering tool 10 includes a removable tubular tip 11 communicating with a metallic riser tube 12. The metallic tube 12 opens into an interior of a solder catcher tube 13. The solder catcher tube 13 is enclosed within a coaxially disposed handle 14. Solder is drawn into the interior of the tube 13 by vacuum applied from tube 17 through conduit 16 behind base member 15. An electrical cord 18 supplies electrical current to a heating element of the desoldering device.
Other prior art devices relate to quick starting operation of an apparatus for providing a source of vacuum. For example, U.S. Pat. No. 4,532,670 to Fortune discloses a device connected between a constant source of vacuum and a desoldering device which serves to boost the degree of vacuum at the desoldering tip upon initial actuation of the vacuum release trigger to facilitate rapid removal of the melted solder. Fortune, however, employs a spring loaded piston to supply an initial pulse of vacuum to the joint. However, this initial pulse is not followed by a steady state application of the vacuum which is needed to effect cooldown of the terminal to thus prevent possible re-sweating of the joint and possible overheating of adjacent components.
U.S. Pat. No. 4,643,776 to Hollowell et al. discloses connecting a 12 volt vacuum pump motor of a battery powered vacuum leaf collector in series with two 12 volt batteries to energize the motor with 24 volts to thereby increase the speed of the motor to provide a higher degree of suction for heavier loads. For lighter loads, the batteries are connected in parallel to provide 12 volts.
Of importance in desoldering is the requirement that the desoldering tip should assume a nearly exactly perpendicular position with respect to the work (typically a circuit board) in order to promote a good seal (e.g., about a plated-through-hole which is filled with a plug of solder) so that molten solder can be aspirated completely, thereby freeing the solder joint. For this purpose, a relatively large, initial vacuum pulse is needed to substantially completely remove the plug of solder while it is still molten.
Further, successful desoldering generally requires continued application, after the initial impulse, of a steady state vacuum to allow the joint to cool down below the solder melt temperature and prevent the formation of a re-sweat joint. Thus, quick removal of molten solder, without stalling of the vacuum pump motor, followed by the application of a steady vacuum avoids unnecessary repeated desoldering operations.